It has previously been proposed--see the referenced U.S. Pat. Nos. 3,465,737 and 3,486,493, Dreisin--to so construct fuel injection systems in which an injection nozzle injects fuel, that the quantity is determined by a hydraulically controlled operating element, introduced in a drain or return line from pressurized fuel being applied to the injection nozzle. The control element, or control slider, controls the effective supply stroke, and thus the quantity of fuel being injected by the injection nozzle pump, by selectively blocking, or clearing the fuel return line from the pump working chamber. This fuel injection apparatus utilizes the control system which is the same for all the injection pumps, and uses a rotary distributor operating in synchronism with the cam shaft of the engine with which the system is being used. The rotary distributor determines the initiation as well as the termination of the fuel injection event. A control sleeve, which is slideable in dependence on the position of centrifugal weights provides for speed-dependent change of the initiation time of fuel injection. The rotary distributor simultaneously acts as a distributor to supply the control fluid to the respective pressure chambers of the control slider or control elements.
A control system of this type, which is mechanically driven, is highly dependent on speed. The quantity of fuel which is injected thus depends, upon changing speed, and on the speed, although the positioning elements were not changed. Such control systems are applicable for high speed engines only to a limited extent. The control fluid pressure line, as well as the fluid line may cause mutual interference, which is difficult to separate, and, if it occurs, undesirably influences control of the quantity of fuel as well as the respective time element of injection.
The earlier Dreisin U.S. Pat. No. 3,465,737 describes a fuel injection system which is similar to that discussed immediately above; a control element or control slider, however, is driven by a separate injection pump forming a control pump, and driven together with the pump nozzle combinations. Change of the timing of initiation of injection is accomplished by providing an injection adjustment element which is included in the drive for the control pump and which transfers a signal representative of drive torque. The arrangement requires much apparatus and, thus, space for its installation.
It has also been proposed in a few injection systems to include a valve element with a magnetic valve arrangement. The injection valve-nozzle combinations themselves are controlled by a magnetic valve. The magnetic valve arrangement is formed as a control slider included in a return, or overflow line. Each one of the injection valve-nozzle combinations have such a magnetic valve associated therewith, which directly affect the injection pressure level. It is extremely difficult to make magnetic valves such that they are all precisely identical, and tolerances of the respective valves, and particularly their operation bases on the applied pressure levels may vary. Thus, if these systems are included in a multi-cylinder engine, the respective cylinders of the engine may not receive the same quantity of fuel from the fuel injection elements, although, from a theoretical design point of view the fuel should be the same. Due to operating tolerances, however, which are practically unavoidable, they may not be.